Aspects of the present invention relate generally to the field of electronic signal processing and more specifically to reducing gain and distortion errors with a correction circuit.
In an exemplary two-stage high performance op-amp, the op-amp's input stage receives a differential voltage at a pair of inputs and generates an output current. The output current is then passed to a second stage. The second stage conventionally receives the first stage output current and a fixed reference voltage at a pair of inputs. The second stage integrates the input stage output current into compensation or integration capacitor, absorbs the input stage current at its output and produces an output voltage. A finite voltage arises at the input of the second stage due to the stage's finite trans conductance. This voltage at the second stage's input generates an error current in the integration capacitor. The generated error current creates an error voltage at the input terminals of the amplifier's first stage that is then amplified to the amplifier's output.
Such voltage error may manifest as gain error and distortion in the amplifier's output which may result in perceptible errors in the data being amplified. Conventionally, this distortion is minimal and was ignored or later compensated for in favor of small and efficient amplifiers. However, high performance circuits are increasingly sensitive to small errors. Accordingly, there is a need in the art to reduce distortion at the output of a two-stage differential amplifier.